In the automobile industry there are many metal components which when assembled overlap one another. This overlapping creates problems both through noise generation due to vibration when the vehicle is in motion and corrosion due to trapped water between the members. In order to eliminate these problems the industry has tried welding or tack welding these components to eliminate the vibrational noise. Additionally, it has been disclosed that application of a sealant between the members or substrates being welded will enhance the elimination of moisture getting between the welded members and causing corrosion (U.S. Pat. No. 4,195,215).
However, the introduction of such sealants into the welding process causes a number of problems for the process. First, due to the nonuniformity of electrical conductivity of sealant, uneven welds may occur even where electrically conductive particles have been introduced into the sealant to reduce this problem. Secondly, the organic sealant often causes the welding electrodes to reach higher temperatures than normally required to weld the materials thereby reducing significantly the number of weld which can be performed before replacement of the electrodes is required and thirdly, the sealant often times is incapable of filling the gaps between the welded members thereby not adequately preventing the introduction of water into this area and therefore not preventing corrosion from occurring.
Sealants which are capable of expanding have been used to bond automobile components together but do not possess the appropriate electrical properties to be practical in weld through operation as they would cause reduced electrode life and a low quality weld.
Therefore what is needed in this art is a pumpable weld through sealant which will not cause the welding electrodes to deteriorate quickly, and will more effectively seal any gap between the welded substrates to more effectively prevent corrosion.